My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
This can be a leak with the transmission fluid.The drain and fill as well as check of the transmission fluid is done with a special tool on this model here from under the vehicle in position 2 in the diagram below.
It requires this special tool here
I would have the transmission fluid checked to see if the level is low and checked for any leaks needing repaired.I have seen the pan gasket leak,transmission cooler line leak as well as front transmission pump seal as possible causes needing replaced.Below is the fill and check procedure for your transmission.
Filling capacity: approx. 9.0 litres
Change quantity: approx. 4.5 litres
1. Place oil collection pan under the transmission.
2. Unscrew drainage screw -1- and drain ATF.
NOTE: Without ATF, the engine must not be started and the vehicle must not be towed.
3. Replacing sealing ring for drainage screw and screw in screw -1-.
Tightening torque: 40 Nm (30 ftlb.)
4. Unscrew the filler screw -2- and fill up ATF with special tool filling system V.A.G 1924 until ATF escapes from the hole of the filler screw.
5. Move selector lever to position "P" and allow engine to idle.
6. With engine running, top up ATF again until excess ATF emerges from the bore of the filler screw.
7. With the brake pedal pressed, change through all selector lever positions, remaining in each position for approx. 10 s.
8. Check the ATF level again and top up if necessary.
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